The present invention relates to X-ray scanning. It has particular application in medical computed tomography (CT) scanning, although it could equally be used in other suitable applications.
X-ray computed tomography scanners have been used in medical imaging for many years. A conventional system comprises an X-ray tube that is rotated about an axis with an arcuate X-ray detector array also rotated at the same speed around the same axis. The patient is placed with their centre of gravity close to the axis of rotation, and moved along the axis as the tube is rotated. A fan-beam of X-radiation passes from the source through the patient to the X-ray detector array.
The X-ray detector array records the intensity of X-rays passed through the patient at each location along its length. From these recorded X-ray intensities, it is possible to form a tomographic (cross-sectional) image, typically by means of a filtered back projection algorithm, if one set of projection data is recorded at each source angle. In order to produce an accurate tomographic image of an object, such as a part of the patient, it can be shown to be a requirement that the X-ray source pass through every plane through the object. In the arrangement described above, this is achieved by the rotational scanning of the X-ray source and the longitudinal movement of the patient.